Fiber optic sensors can be used for many sensing applications, including automotive, medical, security and industrial processing. Fiber optic interferometric sensors can provide the highest performance of any fiber optic sensor, however, fiber optic interferometric sensors require electronic processing to convert the optical information inscribed in the sensor to a linear electrical output. Thus, electronic circuitry is associated with fiber optic interferometric sensors.
Fiber optic sensors are considerably more attractive for sensing applications when the sensor can be remotely deployed with the electronic processing and the reference transducer separated and removed from the sensor. Coherence multiplexing of fiber optic interferometric sensors has been utilized with highly coherent sources as described by Brooks et al., "Coherent Multiplexing of Fiber-Optic Interferometric Sensors," IEEE Journal of Lightwave Technology, Vol. LT-3, No. 5 at p. 1062, (October 1985). Large coherence lengths (.degree. 4.5m), however, are not compatible with small sensor designs. Moreover, these highly coherent sources are typically single mode or quasi-single mode laser diodes.
It is desirable, therefore, and there is described in this specification, a fiber optic interferometric sensor system which utilizes short or very small coherence lengths (on the order of 100 microns) and wherein the reference transducer and the electronic processing circuits are located remotely from the sensor.